ponies twilight is willing to forgive a teenager who brainwashed an entire school and threatened to invade Equestria as an evil demon; a jealous unicorn who enslaved an entire village and forced them all to lose their cutie marks because of a bad experience and created various timelines of apocalyptic Equestria once her plans were ruined; and a draconequus that is literally the god of chaos and brought the entirety of Equestria into peril, 3 TIMES, as well as rendering their main form of defense useless

ponies twilight isn't willing to forgive a stage magician that was just trying to perform in ponyville one time

In Twilight's defense, there was that whole "Return to Ponyville with an evil ancient artifact for the explicit and sole purpose of defacing and destroying Twilight Sparkle" thing...

also, twilight wasn't the one who ruined trixie, nor was trixie the one who did wrong in her debut. Twilight wanted nothing to do with trixie and trixie was a preformer. So while the towns reaction to her (like exiling her) was misplaced and her hatred towards the town for snips and snails mistakes was somewhat justified.